Reclassification of gastrointestinal mesenchymal tumors.

Background: Gastrointestinal stromal tumors - commonly called GISTs - are rare; yet, they represent an important type of mensenchymal tumors arising within the gastrointestinal tract. The acronym GIST was introduced in 1998 to define a well established pathological entity which bears a highly specific marker called KIT (CD117). Scientific interest for these tumors in recent years is mainly due to the progress in identification by immunohistochemistry and the advent of targeted molecular therapy.

Aim: To reclassify mesenchymal tumors of the digestive tract using advanced immunophenotyping.

Methods: We examined the digestive tissue tumors operated at the Principal Military Hospital of Instruction of Tunis over a 19-year period from 1992 to 2011.

Results: We collected 22 cases of benign mesenchymal tumors of the digestive tract. Tumors were initially diagnosed as leiomyomas (4 cases), schwannomas (2 cases), gastrointestinal stromal tumors (14 cases), a leiomyoblastoma and a mesenchymal tumor with fusiform cells. The immunohistochemical study has allowed to correct some diagnoses and, in one case, the block has been exhausted. In total, we selected 18 cases of gastrointestinal stromal tumor, a tumors. The final diagnosis of GIST was confirmed by the positivity of C-kit or DOG1.

Conclusions: The combined use of C-kit and DOG1 ensures accurate diagnosis of GIST. The DOG1 has allowed us to detect the 3 stromal tumors negative for C-kit. This antibody has achieved a diagnostic gain of 15 %. The rate of GIST tumors labeled increased from 71 % to 86 % among mesenchymal tumors.